1. Field of the Invention
The present invention relates to actuators used in disc drive assemblies for linearly moving magnetic heads to different track positions on a magnetic medium.
2. Background of the Invention
Previous designs of linear head actuators use a linear drive motor and a carriage and bearing assembly mounted in series. Because of the series mounting of these components, this configuration requires considerable space in the disc drive assembly.
A different design that has been used mounts the linear drive motor and the carriage and bearing assembly side-by-side. This shortens the overall length, but because of the complex and unsymmetrical structure, significantly lowers the resonant frequency of the carriage assembly, thereby limiting the servo response of the actuator. For medium and high performance disc drives, this limitation has rendered this approach unsatisfactory.
Another shortcoming of some current designs is the use of pivots or mechanisms on the carriage to move a ball bearing on the carriage against a load. The purpose of these preloading pivots or mechanisms is to insure that the carriage always moves along the desired path. Such mechanisms, in which a bearing on the carriage itself is spring-loaded or otherwise adjusted in position, increase the mass as well as the complexity and cost of fabrication of the carriage. These mechanisms, sometimes, have actually resulted in misalignment of the load bearings due to the additional clearances and tolerances involved, and have, in some cases, caused wear on the bearings and guide rods and consequent actuator failure.
Thus, not only do the previous methods and mechanisms used require a large amount of space in order to accommodate them, but other disadvantages including limited servo response due to low resonant frequencies, complexity resulting in increased expense of fabrication and maintenance, and misalignment and wear problems, may also be present.